A conventional connector in the solenoid context provides a connection from a pair of insulated lead wires to the insulated magnet wire of the solenoid coil. This connection is made by having the conventional connector provide a mechanism for penetrating and displacing the insulation of each lead wire and making respective electrical connections between the magnet wire and the lead wire. The conventional connector includes a conductive element, which is electrically connected to the magnet wire of the solenoid. Typically, the conductive element is sized and shaped to essentially cut or bite into the insulation, and contact the conductor, of the lead wire as the lead wire is pressed into the conventional connector. Once the conventional connector has established a connection to the lead wire, it is best not to disturb its position in any way that would disrupt the position of the magnet wire or the lead wire. There are many environments where the connection of the conventional connector is lost because some external force disturbs and moves the conventional connector. The conventional connector may employ a staple to lock the lead wire in place in an effort to avoid loss of electrical connection. However, placement and deployment of the staple can be troublesome and may cause the very disturbance that the staple is supposed to prevent, i.e., due to the force the staple applies to the lead wire.
Typically, the orientation of the conventional connector in the solenoid context is such that the conventional connector is set in a bobbin that forms part of one end of the solenoid coil. The bobbin and conventional connector are located at the end of the solenoid closest to where the lead wire enters the solenoid assembly. This serves two purposes, one being the lower cost by requiring less lead wire length, and the second being the reduction in risk of short circuiting due to the lead wire contacting the magnet wire of the solenoid coil. However, the foregoing orientation is disadvantageous because the connection between the conventional connector and lead wire is susceptible to external disturbances as the connection point is situated close to the lead wire entry point.
The current use of a connector described in U.S. Pat. No. 6,991,488 is directed to insulation displacement techniques of penetrating an insulation jacket and making contact with the internal conductors. A drawback of such insulation displacement techniques, along with soldering techniques, is that the contact is hidden from normal visual examination. This means that usual inspection of the contact is done by measuring the continuity by instruments which are simply connected to the circuit. Although this method can certainly detect open and most bad contacts, it can miss some faulty contacts that will not be sustainable during field use. This is because a meter can only read what is happening at the moment it is being used to make a measurement. The meter cannot predict what will happen in the future nor can it tell if an even slight external jiggle of the wire causes an unreliable intermittent contact.
A good predictor of contact reliability is a visual comparison with what has been proved to be reliable. A skilled artisan, upon visual inspection, would readily recognize a contact which may prove to be bad in the future even though it could pass an immediate meter test.
Another disadvantage of penetrating insulation to make contact with internal conductors is that the insulation compresses into the space between the contact arms, restraining the spring-loaded arm pressure which is desirable for good contact.
A conventional approach to addressing the potential loss of connection is to attach a crimped brass clip to a stripped end of the lead wire. The crimped brass clip may be attached to both the end of the lead wire and an inner starting end of the magnet wire of the coil. The crimped brass clip acts as a key when encapsulating plastic material flows and sets rigidly around the components (including the lead wire) of the solenoid. Although this serves to provide resistance to most external forces, it does not prevent small disturbances to the connection zones which can cause an opening of the connection, such as during thermal cycling or other situations.
Moreover, the crimped brass clip presents a danger of shorting the magnet wire of the coil. A short circuit can occur if the crimped brass clip is located over the outer turns of the coil as extreme heat, pressure, and/or the spurting turbulence of the encapsulating plastic enters and surrounds the coil. Under these conditions, the brass clip may be propelled violently against the outer turns of the magnet wire of the coil and may penetrate the magnet wire insulation. To mitigate this problem, the conventional approach is to provide protective insulating tape over the coil. The theory is that the tape prevents both the short circuit and a stripping of the magnet wire insulation by the extreme heat of the encapsulating plastic. Three thicknesses of 0.007 inch tape has been accepted in the art to be sufficient to protect against short circuits, while one thickness of 0.007 inch tape has been accepted to protect against the melting (stripping) of the magnet wire insulation.
Notwithstanding the above, there is still a potential that the insulating tape will not prevent a short circuit with the lead wire. Further, as the cost of the insulating tape and the installation efforts of same are significant elements of the overall cost of solenoid assembly, there is interest is reducing the amount of tape used. If the probability of shorting is significantly reduced or eliminated, then a significant cost saving is possible by using less (or no) insulating tape.
Maintaining the connection between the lead wire and magnet wire is important for effective operation of the typical solenoid assembly, encapsulated solenoid or any other device where connectors are applied. A loose or completely disconnected lead wire is a common occurrence in a typical solenoid assembly. The current conventional approaches are prone to disconnection due to external forces and disturbances, increase the chance of short circuiting the solenoid coil, and can be costly to manufacture.
Through experimentation, it has been discovered that waggling of the strand of conductor wire as close to the electrical connector as 7.5 mm may cause longitudinal movement up to or more than 0.040″ within the insulation, relative to the insulation and the connector. Such movement is considered a severe disturbance and may lead to disconnection of the electrical connection. When a portion of lead wire that is external to the encapsulation is severely bent, the conductor wires move longitudinally relative to each other and the insulation of the lead wire. This movement is transmitted along the lead wire for a certain length until there is sufficient frictional resistance and distortion of the strands to absorb the movement. If the electrical connection between the electrical connector and lead wire is within this distance, the electrical connection will be disturbed when the lead wire is bent and risk disconnection.
Therefore, there is a need in the art for a mechanism for maintaining a tight and robust connection between the lead wire and magnet wire by connectors.